1. Field of the Invention
The invention relates to improving the transportability of crude oils by pipeline. More particularly, it relates to a two-step process of catalytically dewaxing the crude under mild conditions, followed by filtration to remove a small solids fraction.
2. Discussion of the Prior Art
It is known that some crude oils contain a large amount of wax such that these crudes solidify at ambient temperatures and become difficult to handle in a pipeline or in other modes of transport. With respect to transport by pipeline, the traditional method of solving the problem was to apply heat to melt the wax, followed by pipelining in steam-traced and well-insulated pipelines.
It is not new to filter crude oil. As is taught in U.S. Pat. No. 3,729,414, in the early dewaxing procedures, the wax was crystallized by slow cooling and was separated from the oil by filtering, etc. The earliest process for this purpose was practiced in the oil fields and was called cold settling. A later process applied to light lube distillates involved slowly cooling the oil and filtering to remove the wax formed.
Nor is it new to dewax the crude using a catalyst, such as ZSM-5. This aspect is taught, for example, in U.S. Pat. No. 3,755,138, in which a two-step dewaxing process is disclosed. The process involves (1) solvent dewaxing followed by (2) hydrodewaxing over a ZSM-5 type zeolite.